- Disease must be clinically limited to the esophagus or gastroesophageal junction; if the tumor extends below the gastroesophageal junction into the proximal stomach, 50% of the tumor must involve the distal esophagus or gastroesophageal junction; adenocarcinomas of the distal esophagus would therefore include tumors of the distal esophagus, or Siewert type I according to the Siewert classification, and tumors of the gastroesophageal junction which involve equally both the distal esophagus and proximal stomach, or Siewert type II; tumor must be surgically resectable